@FindBy, @FindBys, @FindAll, @CacheLookup - Selenium API

All are used to mark a field in a page object.
@FindBy: It is an alternative mechanism for locating the element or a list of elements. Used in conjunction with PageFactory this allows users to quickly and easily create PageObjects. (api link)
Example:
    For example, these two annotations point to the same element:
    Syntax 1:        @FindBy(id = "foobar")
                              WebElement foobar;
                              @FindBy(how = How.ID, using = "foobar")  // How is an enum, ID is an Enum constant
                              WebElement foobar;
and these two annotations point to the same list of elements:
    Syntax 2:          @FindBy(tagName = "a")
                               List<WebElement> links;
                               @FindBy(how = How.TAG_NAME, using = "a")
                               List<WebElement> links;
Note: Alternative way of @FindBys: driver.findElements(new ByChained(by1,by2)); (where by1 -> By by1=By.id("");, by2 -> By by2=By.id("");)
@FindBys: Find for all DOM elements that matches each of the locators in sequence.(api link)
Example:
        @FindBys({@FindBy(id = "foo"),
              @FindBy(className = "bar")})
         private List<WebElement> list;
@FindAll: Search for all elements that match any of the FindBy criteria. (api link)
Example:
        @FindAll({@FindBy(id = "foo"),
              @FindBy(className = "bar")})
private List<WebElement> list;

@CacheLookup: as the name suggests helps us control when to cache a WebElement and when not to. This annotation when applied over a WebElement instructs Selenium to keep a cache of the WebElement instead of searching for the WebElement every time from the WebPage. This helps us save a lot of time. (api link)
Example:
        @CacheLookup
@FindBy(how=How.ID, using="foo")
private WebElement element;

Hope this Helps!!!